The present invention relates generally to a fixture and more particularly to a fixture for holding air cooled gas turbine engine blades.
Many conventional gas turbine engine blades have interior passages for transporting cooling air to remove heat from the blades. For instance, some conventional turbine blades have a labyrinth of interior passages through which cooling air is transported to cool the blades by convective heat transfer. Cooling holes in the surface of the blades permit the cooling air to exit the interior passages and form film cooling along the exterior surfaces of the blades. On occasion, the interior passages and/or the cooling holes become blocked, resulting in insufficient blade cooling. Conversely, the cooling holes can be made too large, resulting in too much cooling air being directed through the holes and leaving an insufficient amount of cooling air for other cooling circuits in the blade or for other blades in the engine. Thus, the blades are flow checked during manufacture and periodically at maintenance intervals to ensure appropriate amounts of cooling air flow through each blade cooling circuit.
In the past, a fixture was used to hold the blades during flow check. This fixture included a support for receiving a dovetail of the blade and a clamp mounted adjacent the support which engaged a flowpath surface of a platform of the blade to hold the dovetail against the support. Because the flowpath surface of the blade platform is an as-cast feature, there is significant variation in the distance between the flowpath surface of the platform and the end of the dovetail where cooling air enters the blade. Accordingly, the fixture allowed leakage between the support and the end of the dovetail which resulted in inaccurate flow measurements.
Among the several features of the present invention may be noted the provision of a fixture for holding a gas turbine engine blade having an airfoil extending outward from a shank and a dovetail extending inward from the shank for attaching the blade to a disk of the engine. The dovetail includes at least one pair of protrusions extending fore and aft along opposite sides of the blade. Each of the protrusions includes a pressure face generally facing the airfoil of the blade for engaging the disk to retain the blade in the disk during operation of the engine. The fixture comprises a support for receiving the dovetail, and a clamp mounted adjacent the support for movement between a clamped position in which the clamp engages the dovetail to hold the dovetail against the support and a released position in which the clamp disengages the dovetail to permit removal of the blade from the fixture.
Other features of the present invention will be in part apparent and in part pointed out hereinafter.